关于多线程的一个程序？

Question

本帖最后由 beyondmk2001 于 2011-06-30 19:25:31 编辑

Answer 1

因为你的每个ball的轨迹是相同的，所以你看不出结果
/**
 * 程序中为什么只有1个Ball,为什么左上角会出现一个按钮?
 * 为什么不是一个一个的球在运动,而是1个球在划轨迹?为什么是这样的轨迹?
 * 程序中声明了2个静态final变量STEPS和DELAY,难道没有冲突吗?
 */
import java.awt.*;
import java.awt.geom.*;
import java.awt.event.*;
import java.util.*;
import javax.swing.*;
class Ball{
    private static final int XSIZE=15;
    private static final int YSIZE=15;
    private double x=0;
    private double y=0;
    private double dx=1;
    private double dy=1;
    public Ellipse2D getShape(){
        return new Ellipse2D.Double(x, y, XSIZE, YSIZE);
    }
    public Ball(double x, double y) { //加一个构造方法，改一下轨迹的起点
        this.x = x;
        this.y = y;
    }
    public void move(Rectangle bounds){//move方法不理解
        x+=dx;
        y+=dy;
        if(x<bounds.getMinX()){
            x=bounds.getX();
            dx=-dx;
        }
        if(x+XSIZE>=bounds.getMaxX()){
            x=bounds.getMaxX()-XSIZE;
            dx=-dx;
        }
        if(y<bounds.getMinY()){
            y=bounds.getMinY();
            dy=-dy;
        }
        if(y+YSIZE>=bounds.getMaxY()){
            y=bounds.getMaxY()-YSIZE;
            dy=-dy;
        }
    }
}
@SuppressWarnings(value={"serial"})
class BallComponent extends JPanel{
    private ArrayList<Ball> balls=new ArrayList<Ball>();
    public void addBall(Ball b){
        balls.add(b);
    }
    public void paintComponent(Graphics g){
        super.paintComponents(g);
        Graphics2D g2=(Graphics2D)g;
        for(Ball b:balls){
            g2.fill(b.getShape());
        }
    }
    
}
@SuppressWarnings(value={"serial"})
class BounceFrame extends JFrame{
    private BallComponent comp;
    public static final int DEFAULT_WIDTH=450;
    public static final int DEFAULT_HEIGHT=350;
    public static final int STEPS=1000;
    public static final int DELAY=3;
    public void addButton(Container c,String title,ActionListener listener){
        JButton button=new JButton(title);
        c.add(button);
        button.addActionListener(listener);
    }
    public BounceFrame(){
        setSize(DEFAULT_WIDTH,DEFAULT_HEIGHT);
        setTitle("BounceTread");
        setLocation(458,209);
        comp=new BallComponent();
        add(comp,BorderLayout.CENTER);
        JPanel buttonPanel=new JPanel();
        addButton(buttonPanel,"Start",new ActionListener(){
            public void actionPerformed(ActionEvent event){
                addBall();
            }
        });
        addButton(buttonPanel,"Close",new ActionListener(){
            public void actionPerformed(ActionEvent event){
                System.exit(0);
            }
        });
        add(buttonPanel,BorderLayout.SOUTH);
    }
    public void addBall(){
        Ball b=new Ball((double)Math.random()*50, (double)Math.random()*80); //改一下
        comp.addBall(b);
        Runnable r=new BallRunnable(b,comp);
        Thread t=new Thread(r);
        t.start();
    }
}
class BallRunnable implements Runnable{
    private Ball ball;
    private Component component;
    public static final int STEPS=1000;
    public static final int DELAY=5;
    public BallRunnable(Ball aBall,Component aComponent){
        ball=aBall;
        component=aComponent;
    }
    public void run(){
        try{
            for(int i=1;i<=STEPS;i++){
                ball.move(component.getBounds());
                component.repaint();
                Thread.sleep(DELAY);
            }
        }catch(InterruptedException e){
            
        }
    }
}
public class BounceThread {
    public static void main(String[] args){
        EventQueue.invokeLater(new Runnable(){
            public void run(){
                JFrame frame=new BounceFrame();
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.setVisible(true);
            }
        });
    }}

Answer 2

轨迹就是你的move方法，每次x坐标前进dx，y坐标前进dy，当轨迹超出界限时，把x,y调整，然后dx,dy乘以-1，相当于改变方向前进